LOL. This is not a "line filter", merely a ferrite clamp to pass radiated emissions tests.
To be fair, they also cut down some amount of conducted noise.
EDIT: Note the creative addition of (99.99% likely) fake wire pass-throughs on each side of the clamp, to make it look as though it could indeed be some kind of "inline" filter...
(I'm amazed at how some chinese manufacturers, for instance, are creative with those fake pass-throughs.)
For that to have a sizeable effect on "sound quality" though, the audio section of the laptop should probably have to have been designed with an engineer's feet.
Selling this has a "bonus" is completely misleading anyway, since manufacturers only add ferrite clamps to cables when they are FORCED to after EMI testing, not out of good will.
EDIT2: Given the very probably use of fake pass-throughs, it may also be very possible that the ferrite clamp is not even a ferrite clamp, and may contain absolutely... nothing inside the plastic shell. Would be fun to buy one just to check... and post your result here.